block help

I have a Pontiac YA block with the date code L173. Looking this up it seems to be a 455. I don't have the block casting number yet but can someone help? Everything I look up with just what I have sez 455. Heads are 46's which came on 350's, 400's, and 455's. Help!

 

A YA code would be a 455 block for '73 according to my book.
Pontiac engines from 1968 on have the displacement number cast into the side of the block in front of a freeze plug on the driver's side too.

 

That's what I thought, but it looks like 350 is stamped there. So with an engine cast that late in the year, it would prolly go in a '74 model car correct? So at this point do we decode by what it might go in due to marketing gimmick or stick to the date code cast in and say ok it's a '73 not a '74? Still learning...

 

drivers side front of the block below the head at the front of the side of the block there is a CAST IN # not stamped. What ever that says is what it is.

 

On Pontiac's its cast in behind #8 cylinder, still need to clean it and read it.

 

L173 casting date is a 1974 model year engine.

Looks like it's a low compression 350:

http://www.wallaceracing.com/cgi-bin/engine3.cgi

Year Engine HP Engine code Trans CR Cam Head Code BBL Carb No. Misc
1974 350 155/170 HP YA A 7.6 555 46 1-2 7043062 Block Casting # 488986

 

That was a question I had. Since the block was cast so late in the year would you then refer to codes when the engine would actually be installed (prolly a few months later as in 1974) or stick to when the block was actually cast. That seems stupid and confusing though. Even though the block sez cast in 1973, and 1973 YA blocks in A bodies and B bodies were 455's, in the F body it was a 400, now you are saying that it should be treated as a 1974 350 that was made in 1973? So when I do finally get the block casting code it will read 488986 (350) and not 485428 (455)? Please explain this Martian logic to me. I mean what is the purpose of putting a date on a casting then referring to a different year?

 

Is it a bare block? Can you measure the bore? You should be able to tell the difference between a 350 and a 400/455 even with a ruler.

 

The casting dates are useful, but you just have to remember that the model year is not the same as the calendar year.

The new model production schedules usually began in mid to late summer, so any parts cast after late July or early August were for the subsequent model year.

In your case, a late (L=November) 1973 casting date is definitely a 1974 model year part. If it was a service block for the 1973 or earlier model year, it would NOT Have a production code (YA); it would only be stamped as a service replacement block (SR).

 

That would make sense as the new models start in september and they would need the assembly hardware before that for production. UNLESS of course was a 1/2 year total makeover production change THEN it could be before september but still for the following year.

 

I spent 31 years at GM and in a couple of major supplier companies. Throughout the 1990's (and even up to today, in most cases) it was very unusual to have any model year change-overs that varied from the "normal" July/August schedule.

Vehicle assembly for the "new" model year started after the summer shutdown periods, usually in early July. They required enough lead time to fill the dealerships and distribution networks with new vehicles before the official introduction dates, which were normally in September.

Vehicle assembly and component manufacturing schedules had to begin well ahead of the early September introduction dates. In the manufacturing plants, we would typically "build out" of the current model year in June, then perform the required engineering and process changes for the new model year parts. First new model production for big components like engine blocks, transmission cases and other long-lead items were in June or July.

Mid-year launches had different dates, but you get the idea...

In this case, an engine block cast in November, 1973 would be a 1974 model year engine. In fact, a November casting is almost half way through the 1974 production year.

 

OKAY! Well I guess then what I have here is a garden variety, 2 bolt, 2 barrel, 650 lb piece of low compression 150 hp crap. Hell the stock 326 made 100 more hp than this thing. So what can I do with it? I mean with the cost of machining it into something bigger as in a 455 wouldn't be better off getting a rebuildable 455 to begin with?

 

I guess that all depends on how easy/cheap it is to find a good 455 core to start with.

 

Most Pontiac guys will tell you not to spend money on a 350 because it will cost as much to rebuild a 350 as it costs to build a 400 and the 400 will significantly outperform the 350.

You CAN, if you want to stick with your original block, get a stroker kit to turn the 350 into a 383. It's pretty big $$$, but its feasible.

Building a 400 with a newer style cam (designed to build good torque and power while living on today's pump gas) is probably the most cost-effective route if you look at power/cost trade-off.

If your 350 runs well, I'd keep it running. Add a 4-barrel intake manifold & carb, add true dual exhaust and drive it and have fun with it while you keep you eyes open for a good deal on a 400 or 455. The intake manifold, carb and Ram Air manifold or headers will fit any "D-port" 350/400/455, so you can use them on your upgrade engine!

The 455's are great (no substitute for cubic inches!), but they are getting expensive. If you can find a deal on a 455, that might be the best possible solution.

Also, you can't compare the HP ratings from the early 60's to those of the later engines. Until 1972, advertised HP was based on "Gross" output. The engines were rated without any accessories, tested on a dyno with optimal timing, free-flowing headers or exhaust manifolds with no mufflers or pipes, no transmission or other pumping/parasitic losses. The ratings changed to SAE "Net" measurements in 1972. The result was a reduction of (typically) 20% to 30% in advertised HP and Torque outputs. There were also other changes occurring at that time (early emissions controls, reduced compression ratios), but the change in measurement methods was the biggest single factor in the rating changes.

The base 2-barrel Pontiac 350 (9.2:1 compression ratio) was rated at 265HP and 355Lb-ft Torque. Your 74 would be slightly less powerful than the 68 due to a different cam profile and reduced compression ratio.

 

I'd go with an LS engine and a Tremec six speed.
That's if you don't care about pulling stumps or having it looking original under the hood.
They've been putting the LS in '66 Goats for years. There's plenty of info on how to do it and parts available for the conversion.
Be way better on gas than a 455??